The present invention relates generally to a solar power plant, and more particularly to heliostat arrays in a central receiver solar power plant having multiple receivers.
Economic performance of a solar power plant improves when the energy in sunlight is collected and converted to a useable form with increasing efficiency. The economic performance of a solar power plant also improves when costs of manufacturing, installing, operating, and maintaining the elements of the plant decrease.
A central receiver solar power plant, also known as “power tower” architecture, has a tower-mounted receiver for collection of sunlight and conversion thereof into heat or electricity. Sunlight is concentrated on the receiver by reflection from heliostats spaced about the tower and located near ground level. Each heliostat has a mirror whose orientation is adjusted continuously to reflect sunlight toward the receiver. Efficiency of reflection of sunlight from a heliostat is affected by several phenomena, including the position of the heliostat relative to the tower and blocking and shading effects by adjacent heliostats. An arrangement of heliostats along tower-centered arcs, with progressively larger arc-to-arc distances and a staggered configuration of heliostats from arc to arc, has been the heliostat layout choice for central receiver plants, in both research and development and commercial settings, for example, as described in U.S. Pat. No. 4,365,618. In some plants, the heliostat array is bounded by a circular sector; in others, the sector spans a full 360 degrees around the tower.
However, economic performance of a solar power plant further depends on the cost of installing, maintaining, and operating the power plant, as well as the cost of the land occupied by the power plant, per unit of output power. Locating the heliostats of a central receiver power plant in the multiple arc manner leads to an installation process that is complex, difficult to survey, and irregular and costly in its installation. Additionally, parcels of land are generally available in rectangular areas. Thus a solar power plant with a circular (or circular sector) field of heliostats will not properly “nest” in a rectangular parcel of land, and thus yield a poorer land utilization for the entire plant. Accordingly, it is desirable to create a solar power plant that efficiently collects solar energy and is cost-effective to install.